Don't expect Russia to make stupid attacks on NATO countries because it would be pointless. Do expect Russia to reclaim its former sphere of influence which includes eastern Ukraine which historically was the original Russia.
Oh, that's alright then - to invade a sovereign country, stage a corrupt referendum, and to fund and supply 'rebels' in the Eastern Oblast of self-same sovereign country? And let's not forget the 'collateral' damage in such an adventure - such as the downing of a Malaysian airliner - and don't come back with tosh about it being shot down by the UKN AF!
On that basis, and using your logic,
England would be well within its rights to occupy Normandy, Calais and Brittany on the basis of an historical connection and, err, 'sphere of influence'. How, on Earth, can the Russian invasion of Crimea be supported by State Practices and norms of International Law